1. Field of the Invention
The present invention relates to an image forming apparatus provided with a developing unit that includes a feed opening through which toner is supplied from a toner cartridge and that visualizes a latent image formed on a photosensitive drum in order to form a toner image.
2. Description of the Related Art
In a developing unit provided in an image forming apparatus, after toner stored in the developing unit is decreased, toner is typically supplied to the developing unit from a toner cartridge. For example, toner may be supplied to the developing unit through a feed opening that is laterally provided in the developing unit, or through a feed opening that is provided in the top of the developing unit.
A paddle that agitates the supplied toner to feed the toner in a direction of a photosensitive drum may be provided in the developing unit. The paddle is configured to rotate about a rotary axis. The feed opening is provided only in a central portion in a direction of the rotary axis of the paddle and does not extend over the total length of the paddle. Because toner is supplied only from the central portion, an amount of toner is not evenly distributed in the axial direction, thereby generating unevenness. That is, a large amount of toner exists near the feed opening while small amounts of toner exist in both end portions in the axial direction. The uneven distribution of the toner is exhibited as unevenness in the density of the formed image, thereby degrading image quality.
Alternatively, the feed opening may be formed over substantially the total length in the direction of the rotary axis of the paddle. When the opening length of the feed opening is increased in this manner, the problem of uneven distribution of toner is solved. However, a shutter mechanism that opens and closes the feed opening must be enlarged, thereby generating a problem in the strength of the casing.
In view of the foregoing, an object of the present invention is to provide an image forming apparatus that can evenly diffuse toner without increasing the opening length of the feed opening.